For this purpose, the oil level regulator has a suitable sensor that measures the oil level in the machine. When an oil deficiency is determined, a controller opens a solenoid valve in order to supply the machine with oil from a reservoir. In the INT 280 B® oil level regulator of the present applicant, during refilling of oil a filling period, comprising a filling cycle in which oil is refilled during a filling cycle period, and a pause cycle in which the refilling of oil is interrupted during a pause cycle period, is repeated until a sufficient oil level is reached. In the INT 280 B® oil level regulator, the filling cycle period and the pause cycle period in the first filling period each last for 5 s. In the next filling period, the periods are 10 s each, then 20 s each, and lastly 30 s each. The most recently achieved filling period (30 s filling and 30 s pause) is maintained until a sufficient oil level is reached. In this known oil level regulator, the cycle periods are fixed.
The quantity of oil refilled during a given filling cycle period varies very greatly with the prevailing pressure with which the oil is refilled. For refrigeration system compressors, operations were carried out in the past at oil pressures in the range of 30 to 50 bar. With the increasing use of carbon dioxide as a refrigerant, the pressure ranges from compressor to compressor vary significantly more than formerly. Transcritical CO2 compressor facilities may thus be operated at a pressure of up to 130 bar.